A key prediction in the study was that if the court is unbiased, the error percentage should be independent of the victim’s race. In the U.S., all first-degree capital sentences are automatically appealed. With this fact in mind, the researchers then explored lower court errors, corrected by superior courts. The study highlighted errors that were reversed by higher courts, with the assumption that those courts were only improving errors of accuracy, and therefore, racial bias would be removed.

Incongruously, the study found “robust evidence of bias against minority defendants who killed white victims: in Direct Appeal [first appeal stage] and Habeas Corpus [the final stage of revisions and appeal in Federal Court].” Minority defendants convicted of killing white victims were 9 percent more likely to see their sentence reversed by a higher court than in cases involving a minority killing another minority.

The researchers also found that superior courts have less racial prejudice or no prejudice.